1. Field of the Invention
The present disclosure relates generally to automatic hand brakes and more specifically to an automatic release of hand brakes control system.
2. Description of the Related Art
Hand or parking brakes on rail vehicles generally include a chain connected to the vehicle brakes and wound around a wheel. The brakes are applied by rotating the wheel and tensioning the chain. The hand brake includes a trigger or lever which, when activated, automatically releases the tension on the chain and releases the parking hand brake. To make sure the hand brake is fully released, the release mechanism has a prolong release mechanical structure.
Two cylinders may be provided on the hand brake to apply the brakes by turning the wheel to tension the chain and a second cylinder to release the brakes by interacting with the release trigger or lever. A pneumatic system to control the two cylinders and the use of parallel manually actuated valves and electro-pneumatic valves are illustrated in U.S. Pat. Nos. 6,394,559 and 7,014,275, for example. The apply and release cylinders are activated by the manual valves as long as the manual valves are activated to connect a source of pressure to the cylinder and for a short period there after determined by the choke on the exhaust port of the manual valve.
The actuation of the electro-pneumatic valves as discussed herein may be by an electrically controlled pneumatic (ECP) brake network and through the cars control unit (CCU). The overall control system is described, for example, in U.S. Pat. No. 7,073,753. Remote control of the hand brake by hand-held terminal is described in U.S. Pat. No. 6,175,784.